C1 catalogs, vs. LR

I'm a long time LR user looking at alternatives. I really like C1 - but I'd be giving up one of my big reasons for leaving LR, which is the big unwieldy catalog file. I use MS OneDrive for backup, and if I put the catalog in the OneDrive folder it will be automatically synced to the cloud - but that means uploading the whole file on every edit session, not acceptable given my low upstream bandwidth. If I position it outside of the synced folder tree, I have to somehow remember to back it up.

I see that C1 has a "session" model as well, but it's not dead simple and it would take me some time to completely understand the pros and cons of this alternative.

Are C1 catalogs big and monolithic, like LR? Is there an option to perhaps use sidecar files for edits?